#9 - Rifka: We do not need to stop and ask for directions.

[PresidentLSAT]

Thanks guys,

I identified the premise as "If we are lost, we ask for directions." That's not something Craig disagrees with. The difference is their opinions on whether they are lost or not. That's more implied which will work for B but "If we are lost, we ask for directions" looks like a premise we can support and they both agree on this, leading me to C. I figured why pick an assumption when there is a premise I can support. Is there something I'm missing here?

[Jeff Wren]

Hi PresidentLSAT,

First, the correct diagram for Rifka's conditional statement is actually:

Need to stop and ask directions -> we are lost

(If we need to stop and ask directions, then we are lost.)

And the contrapositive would be:

Not lost -> We don't need to stop and ask for directions

(If we are not lost, then we don't need to stop and ask for directions.)

This contrastive is what Rifka uses (along with the assumption, also called an implicit premise, that they are not lost) to draw the conclusion that they don't need to stop and ask for directions.

Diagramming "unless" conditional statements can be tricky. We discuss how to diagram them in lesson 2 of our LSAT course and in chapter 6 of The Logical Reasoning Bible.

You are correct that Craig doesn't dispute the premise "if we are not lost, then we don't need to stop and ask for directions." The problem with Answer C is that it states that Craig accepts the truth of Rifka's "premises" (plural) rather than just one premise (singular). That one tiny difference between plural and singular makes this answer incorrect. That is very tricky and requires very careful reading, which of course is one of the main skills tested on the LSAT. Craig doesn't accept Rifka's other premise, the implicit one, that they are not lost.

[Mo28_28]

Hi
Could you clarify what is the meaning of implicit premise and its application in this argument?
And why E is not correct?
Thanks.

[Dave Killoran]

Hi Mo,

The explanation is actually in Jeff's (and others on the prior page) comment immediately above: "along with the assumption, also called an implicit premise." An Assumption is an unstated premise, and an implicit premise is the same as an unstated premise. The implicit premise being referenced is that Rifka doesn't think they are lost, Craig does.

Biggest problem with (E) to me is that Craig is not at all noncommittal about the conclusion; instead, he clearly disagrees with Rifka's conclusion.

Thanks!